Fixed Network for an Automatic Utility Meter Reading System

ABSTRACT

A fixed network for automatically reading a utility meter system has been developed. The network includes multiple meter interface units (MIUs) that each collect data from a designated utility meter. The collected data is transmitted to a primary data collector. The network includes multiple data collectors and each MIU identifies its own primary data collector based on signal quality between the collector and the MIU. The network includes a central host computer that is used to receive the collected data from the primary data collectors.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is divisional of, and claims the benefit of andpriority to, U.S. patent application Ser. No. 12/178,541 filed on Jul.23, 2008, which is a continuation-in-part of U.S. patent applicationSer. No. 11/964,001 that was filed on Dec. 24, 2007 which is acontinuation of U.S. patent application Ser. No. 11/758,661 that wasfiled on Jun. 5, 2007 entitled “Fixed Network for an Automatic UtilityMeter Reading System” which claims priority from U.S. Provisional PatentApplication No. 60/803,926 that was filed on Jun. 5, 2006 entitled“Fixed Network for an Automatic Utility Meter Reading System”.

FIELD OF THE INVENTION

The invention relates generally to automatic utility meter systems. Morespecifically, the invention relates to a fixed network for an automaticutility meter reading system.

BACKGROUND ART

Meters that measure utility usage are widely used to keep track of theconsumption of an end user. For example, utility companies that supplywater to their customers typically charge for their product based onusage. Usage of water is typically measured by a meter that is installedfor each individual customer on their respective water supply line. Autility company employee periodically (usually once a month) manuallycollects the reading from the meter. These readings are usuallycumulative, so the amount of usage for the present period is calculatedby subtracting the reading from the previous period. Once the usage iscalculated, the customer is billed for that amount of water used duringthat period.

Manually reading usage meters is labor intensive, time consumingexpensive, and subject to human error especially for residentialcustomers because each meter monitors relatively little usage ascompared with larger, commercial customers. As a result, meters combinedwith electronics have been used to allow for quicker, more efficient,and more accurate collection of usage data along with other pertinentinformation such leak information or reverse flow detection. Theelectronic meters may still measure usage by monitoring flow through aconventional, mechanical meter. The usage readings are storedelectronically and then transmitted via radio signals to a localtransmitter/receiver operated by the utility.

The transmitter/receiver that receives the data from the meter istypically a mobile receiver that can be handheld or vehicle mounted. Autility employee drives or walks within proximity to the meter and themeter data is received and stored in the transmitter/receiver. Whilethis system is an improvement over a manual meter reading by anemployee, it is still labor intensive in that it requires an individualto transport a transmitter/receiver into range of the electronic meter.Consequently, a fixed communications network for automatically readingutility meter data is desirable.

SUMMARY OF THE INVENTION

In some aspects, the invention relates to a fixed network for utilitymeter reading system, comprising: a plurality of meter interface units(MIU), where each MIU collects data from a designated utility meter; aplurality of data collectors, where each MIU identifies and establishesa communication link with a primary data collector that has beenidentified as having optimal signal quality with the MIU; and a centralhost computer that receives the data from the plurality of datacollectors.

In other aspects, the invention relates to a fixed network for utilitymeter reading system, comprising: a plurality of meter interface unitswhere each MIU collects data from a designated utility meter; aplurality of data collectors that receives the data from at least oneMIU; means for identifying a primary data collector for each MIU fromthe plurality of data collectors based on signal quality with the MIU;and a central host computer that receives the data from the plurality ofdata collectors.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

It should be noted that identical features in different drawings areshown with the same reference numeral.

FIG. 1 shows a schematic of a fixed network automatic utility meterreading system in accordance with one example of the present invention.

FIG. 2 shows a diagram of a 24-hour transmission schedule for the systemin accordance with one example of the present invention.

FIG. 3 shows a sequence diagram of a data transmission packet inaccordance with one example of the present invention.

FIGS. 4 a-4 d show detailed sequence diagrams of various examples oftransmission packets in accordance with the present invention.

DETAILED DESCRIPTION

A fixed communications network for automatic reading of utility metershas been developed. FIG. 1 shows a schematic of a fixed networkautomatic utility meter reading system in accordance with one example ofthe present invention. In this example, the network is used for a waterutility system. However, other embodiments of the invention describedthroughout this document can be used for other types of utility systemssuch as gas or electric. In these embodiments, data for each type ofutility may be transmitted on different frequencies. In FIG. 1, a systemof mechanical water meters 8 are shown attached to a corresponding meterinterface unit (MIU) 10. The MIU 10 is an electronic unit that collects,analyzes and stores data from the meter 8. In alternative embodiments,the MIU may be integrated into the meter rather than a separatecomponent. The MIU 10 includes a radio transmitter/receiver thattransmits the data to a collector 14. In this example, the collector 14is mounted on a telephone pole. A collector 14 receives, analyzes, andstores the data from multiple MIUs 10. In some embodiments, thecollectors 14 are arranged so that each MIU 10 is intended to be incommunication with at least two collectors 14 in order to provideredundancy in the system communication links. In the case where multiplecollectors are in communication with an MIU, the MIU will identify thecollector to which it will transmit its data by use of signal quality orsignal link integrity. Occasionally, a single isolated MIU 10 may belocated in an area so that it can communicate with only one collector.Once the collector receives the data, it is transmitted to a centralhost 20 computer that is maintained by the utility. In this example, thecollector 14 communicates with the host 20 over telephone lines.However, in other embodiments, other methods of communication could beuse such as radio, internet, intranet, wide area network (WAN), etc. Itis beneficial to embed multiple links between the Host and collector. Ifone connection fails then the Collector or Host can switch to analternate media for communications. This improves system performance andreduces impact of a single failed link. An example is a collector withand integrated high power radio and WiFi options that monitorsacknowledgment success from the host and decides to switch between radioand WiFi back haul communication.

The collectors have a receiver in them for receiving the RF signal fromthe MIU, in some embodiments, the collectors include a transmitter ifthe system is setup for 2-way communications between the collector andMIU. This receiver (and transmitter in the two way systems) in thecollector can be used as an communications link between collectors inaddition to or as a back up to the wide area communications link. Oftenthe system is not operating at full capacity. This allows use of thisradio as an alternative communication link which in turn saves cost.

In other embodiments, collectors may be located on water towers to gainthe height needed to provide a possible three-mile grid. However, it isadvantageous to use communications at the longest possible effectiverange since this reduces the number of collectors needed to service thesystem. Alternate locations may be on cellular telephone towers, watertowers, and other similar utility structures. In some embodiments, thewater tower may be used as a reflector for use with a ground basedantenna. Public buildings may be suitable in high-density applications.The MIUs may be located on a residential house wall, in an indoorbasement, or in a meter pit or vault location or other suitablelocation. The host will typically be located in the utility main officewithin the IT department or billing organization.

Some alternative embodiments may use repeaters to retransmit data withinthe system. Typically, additional collectors will perform the repeaterfunction. In other embodiments, a lower cost repeater may be used toallow reception and retransmission of a few end points that cannot bereceived directly by the collector. The repeater will use a similarprotocol as the collector when communicating to the MIU and willencapsulate the MIU transmission and forward it to the Collector.Repeaters may be located at lower heights such as utility poles andpublic buildings or private residences.

High-density networks are defined as networks where the number of MIUsper collector is between 10,000 and 50,000. For densities up to 50,000MIUs per collector, a 3-mile grid would be acceptable. For densitiesgreater than this, collectors typically cannot meet the three-mile gridrequirement without special modifications of the system components.Possible modifications of the system include: reducing the heightinstallations with smaller grid size; conducting full duplex operationof the transceivers with separate transmit and receive paths; usingmulti-channel collectors where each collector uses multiple transmit andreceive frequencies; and using directional antennas that are dedicatedreceivers to a specific segment of the grid. Low-density applicationscan typically conform to the 3-mile grid performance requirements withno system modifications required. However, it may be possible to usedirectional gain antennas in these applications to increase the gridsize in the preferred direction.

When an MIU is first being installed by a utility technician, thetechnician activates the MIU with a “magnetic swipe” or other suitablemethods of activation. The MIU will respond to the activation byproviding a data message with configuration information to thecollectors. After activation, the MIU will listen to the collectormessages for a period of time. It will use the collector messagestrength to determine the best link. The MIU will communicate the magnetswipe packet to the collector with the best link margin. In alternativeembodiments, the MIU will simply listen for a Collector'sacknowledgement signal (ACK or ACK packet) or Time of Day and signal anduse this to determine the preferred collector prior to transmitting theconfiguration packet. In other embodiments, the MIU can be made to use aspecific collector by updating the configuration table of the MIU viathe Collector or a hand held programming device used during theinitialization process.

When the utility technician is in the field at a given MIU location, theservice person usually needs to know if the MIU is functional, correctlyconnected, and in communication with the collector. Typically theutility will activate the MIU and it will read the register and transmitinformation to the collector. The technician has as portable receiverthat receives the MIU transmission that was sent to the collector whichindicates the performance of the MIU. The receiver then listens for aresponse from the collector to know if the collector received the MIUtransmission. Additionally, the collector's message can includeadditional information such as the S/N ratio, etc.

In other embodiments, the collector can send (either directly or throughanother computer such as the host) an e-mail, or text message when a“magnet packet” is received. This packet is sent for testing purposes.Alternatively, the collector or host computer can send an e-mail or textmessage when an ID number is received that is not in the system.Alternatively, an e-mail or text message can be sent when an ID numberis received that has been listed.

The network may operate in either a “one way” mode or a “two way”communication mode between the MIUs and collectors, or a combination ofboth. In the one-way mode, the MIUs transmit to the collectors and donot receive communications from the collector in return. One-way MIUswill randomly transmit up to four times per day. This rate allowscollection of 99% of the readings each day. One-way MIUs will bereceived at any collector and the data forwarded to the host. Readingswill be current at the time of transmission. The collector will timestamp all received MIU data. The host will gather the data from eachcollector and create a unique data entry that incorporates the timereceived, the number of times received and which collectors received thepacket.

In a two-way mode, the MIU and collector communicate back and forth witheach other exchanging data, status requests, system instructions, etc.Communication from a collector to the MIUs may be simplex, half duplexor full duplex for two way enabled MIUs. Readings will be taken at afixed time during a 24-hour period. The MIU does not have to transmitthe time of read because the system knows the time the MIU is programmedto take the reading (typically at midnight or “zero hour”). Once theconsumption data has been transmitted the MIU will listen for a verybrief period (approx. 10-30 msec) to receive an acknowledgement and anyspecial communications schedule. MIUs will remain in sleep mode up untilthe scheduled read or communications time.

The collector will transmit the data received from the MIUs to the hostcomputer. An MIU can store 6-hour reads for one day or daily reads forthree days. The collector can store the reading information for 3 days.The host normally receives at least one reading a day, but more can berequested. In addition hourly consumption data can be requested. If thelink to the host is ever lost, the collector will continue receivingdata from the MIUs and store in the non-volatile memory until the linkto the host is re-established. Once reestablished, the data can betransferred. The collector will keep a record of all data for threedays. The collector will also keep a record of when it was disconnectedand when communication was restored communication to the host.

In a typical system operation, a collector would be installed withcontinuous two-way communications between itself and the host computer.As MIUs are installed, the MIU will transmit a configuration packet withcontaining identification and initialization data from the MIU. The MIUID will incorporate the type of meter data (e.g., water, electric, gas)that is being transmitted. At this point, the MIU would assume it isoperating in the “one-way” mode. During installation the MIU initiallywill listen to the collectors transmitting on the channel in response tothe configuration data packet. Each reception from a collector will havethe received signal strength (RSSI) logged. The MIU will record thevalue of up to four transmissions from different collectors that arehaving adequate transmissions within a timeout period. Once the signalstrength values are collected, the MIU will record the top two (if twoare found) and use these as its primary and secondary collectors. Theprimary collector will be the one that the MIU will normally transmitwith and establish a signal link of an optimum power. The secondarycollector would be the collector that the MIU transmitted to as a backup in case of a link timeout. If no collector is active, the MIU willenter the fall back state where it assumes one-way communications. Itwill typically try to reestablish communications with the collectorsonce per day.

In an alternative embodiment, the MIU will listen for an initial “timemessage” transmission from a collector. If one or more collectors weredetected, the MIU would store the identification (ID) of the threecollectors with the strongest RSSI. After a specified time interval, theMIU would transmit at full power (typically 1 Watt), identifying itselfas operating in a two-way mode and identifying the collector thatreceived with the strongest signal (if there was one). The MIU wouldlook for an acknowledgement signal (ACK) from the collector. The MIUwould transmit 3 additional times, each time looking for an ACK. If noACK was received, the MIU would attempt to establish communications oncewith each of the additional collectors it initially detected. If no ACKwas received from the additional collectors, the MIU would go to theone-way mode of operation. If an ACK was received from a collector, theMIU would set its clock, and switch to the two-way mode of operationwith that collector. If at any time the MIU cannot successfully operatein the two-way mode, it will automatically revert to the one-way mode.This is the “fall back” position of a one-way system for the network.Each transmitter would send in the reading 2 to 4 times at random timesduring a day. The collector would always be listening. If at any timewhen operating in the one-way mode, the MIU will switch to the two-waymode if it can successfully communicate with a collector. If the hostsystem detects the loss of 2-way operation between collector and MIU, itwill attempt to reassign the MIU to a specific collector in addition tothe MIU's attempts to reacquire a collector periodically and become twoway again.

For example, during the normal mode of operation with randomtransmissions, the MIU transmits at a random time the data reading andidentifies the collector from which it is expecting an ACK. The MIUturns on its receiver for up to one minute. After successfully receivingthe reading, the collector will send an ACK to the MIU along with anyadditional commands desired. If no additional commands were received,the MILD would turn off the receiver until the next time it is supposeto send in a reading. This would normally be the next day. If (noacknowledgement) was received, the MIU would resend the reading. Ifnothing was received after retransmitting multiple times at randomintervals, the MIU would assume it was suppose to revert to the one-waymode. Each time a reading was transmitted, the receiver would be turnedon to look for a command or ACK, in which case it would switch to thetwo-way mode.

The MIU and collector may optimize their communication link to allowlower power transmissions where possible. This avoids collector overloadand help to prevent signal collisions among collectors and MIUs. Thiswill also help to extend the battery life. The collector receiversensitivity and/or transmit power may also be optimized based on theRSSI reading from MIUs. In a typical optimization procedure, the MIUtransmits a message at full power that includes flag indicating it is atfull power. The collector receives the MIU message, measures the signalto noise ratio, and sends ACK and command for MIU to reduce power forits next signal. The MIU receives ACK, the reduction command andmeasures RSSI. On the next transmission by MIU, it transmits at reducedpower. The MIU's message indicates the amount of its power reduction andmay include a command telling the collector the amount to reduce itspower by. The collector transmits ACK and includes an indication thatthe power has been reduced. If the MIU fails to hear the ACK whichindicates either the collectors power was reduced too much or the MIUspower was reduced too much), the MIU reverts to full power on the nexttransmission and the sequence starts over. During typical operations,the MIU may conduct periodic surveys of the strength of systemcommunications links. Typically, the MIU will log the last fourcollector RSSI values and perform a running average of signal strength.If the margin for the communication link between the MIU and collectoris ever below the specified value, the MIU renegotiates the link bytransmitting at full power and updating the link values.

In alternative embodiments, the MIU may select the collectors based onthe signal to noise (S/N) ratio rather than signal strength alone. Thishas the advantage of selecting the most efficient communication linkbetween an MIU and a collector. For example, a collector with thestrongest signal may not have the best data transmission quality if ithas a high volume of noise present. Conversely, a collector with lowersignal strength but with a very low noise presence may provide the bestdata transmission clarity. In an alternate embodiment, the MIU may usethe signal to noise ratio measured from the collector's transmission toadjust the power the MIU uses for its transmission. This is similar tothe operation described previously but collector does not adjust itspower.

Having the MIU responsible for selecting the best collectorcommunications link reduces the burden on the system and makesassignment of MIUs and collectors automatic during installation. Datatransmission is controlled at the MIU level with alarms and readingsbeing sent at the time selected by the MIU. This improves scheduling ofdata transmissions between the MIU and the collector. Additionally,having the MIU control the link selection, transmit power, transmitscheduling and alarms has many other benefits. This distributed controlenhances the network performance by reducing the burden on the remainderof the fixed network system operation and management. Battery life forMIU is improved by reduced collisions and retransmissions. It alsoincreases the probability of successful communications by having the MIUmanage the link selection and retransmissions during communicationsproblems. Installation is more automatic since no prior configuration ofthe host or collector system is required to assign the MIUs to acollector.

In some embodiments, the host computer controls the synchronization ofthe system clocks of the various components. The collectors will receivetime stamp information from the host computer. It should be updated on adaily basis. Under normal operation, the collector will transmit to theMIU the correct time at least once every 24 hours. The MIUs will receivetime stamp information during acknowledgement message from thecollector. In addition, the collector will transmit global time messagesperiodically such as once per minute if no acknowledgements are sentfrom the MIUs.

Two way MIUs will transmit their daily data and alarms on a random andpossibly slotted basis except during the Administrative slot periods.Administrative slots are defined as periods where the network performsdiagnostics, configuration and program downloads. FIG. 2 shows a diagramof a 24-hour transmission schedule for network. The four-hour segmentlabeled “System Window” is the administrative slot period. Nounrequested data transmission from the MIUs takes place during thiswindow as it is reserved for communications regarding systemmaintenance. Instead all normal data transmissions from the MIUs will inthe twenty-hour segment labeled “Transmit Window”. The System Window canalso include the time to transmit the RF call sign (CWID). The modern inthe collector can be programmed to transmit the call sign using standardcall sign methods. The modem can use specific bit patterns that resultin meeting the call sign requirements.

In this example, there are two activities that are timed in the MIU on a24 hour basis. One is the reading cycle and one is for the transmitcycle. The read cycle can provide five reads per day on a 6-hour basis(four 6-hour reads and a Daylight savings time read) or a flow profiletransmission of the hourly usage percentage for the entire day. The MIUcollects the reads and stores the reads prior to the Zero Hour read. Atthe time of the Zero Hour read, the consumption of the previous readwindows is calculated and stored in a buffer to be transmitted. The readcycle then resumes. After the Zero Hour reads are stored, the MIUcalculates the time of the next transmission using four time windowswith a random transmission within each window. The formula for thetransmission delay value is: T1=INT (RND*Tmax1). Tmax1 is the maximumduration in tenths of seconds of the first transmit period. IND is arandom number between 0 and 1. INT is the integer function. There arethree other possible retransmissions that use similar formulas. Thefirst retransmission delay is: TR1=Tmax1+INT (RND*Rmax1). The secondretransmission delay is: TR2=Tmax1+Rmax1+INT (RND*Rmax2). The thirdretransmission delay is: TR3=Tmax1+Rmax1+Rmax2+INT(RND*Rmax3).

In one example of a typical two-way operation mode, the MIU collectsfour readings a day. Then after the six hour reading (or the twelve hourreading on a small system), the MIU starts transmitting its data at thestart of transmit interval and transmits all readings at once. In someembodiments, the specific data transmission time is based on the Alohamodel using a transmission time interval of 4 hours. When dealing with afixed network system with multiple collectors and a large number ofMIUs, the challenge is to structure the transmission times so as tominimize interference between transmitters. The transmitters use theAloha method to determine when to transmit. This is a common andwell-known practice in radio frequency meter reading systems.

In the normal use of Aloha, a random number is generated based on somepre-determined time period. This random number then determines when theunit will transmit within that time period. As soon as the unittransmits, another random number is generated, and a new transmissiontime is determined within that time period. The present inventiondiffers and improves on this concept in several ways. First, an initialtime period is established each day. The random number determines whenthe transmission occurs during this time period. As soon as the unittransmits its data, another random number is generated. However, therandom number is used to determine when to transmit during the secondsubsequent time period. In other words, a unit will only transmit onceduring any time period. This “modified Aloha” procedure is continueduntil a successful transmission of the data has occurred.

The values of these transmit and retransmit periods have optimum valueswhich allow the highest percentage of reads to be acquired during thetransmit period. These values can be found in an interactive processthat varies each period in value and finds the resulting optimum value.Thus the initial transmit period and each retransmit period value isoptimized to allow the highest number of readings to be transmitted byMIUs to the collector during the transmit time.

If multiple retransmissions of data from the MIUs are frequentlyrequired, the MIUs may need to reconfigure the communications links withthe collector. In some embodiments, a rolling seven-day window is usedto keep track of the number of retransmissions required between acollector and an MIU. If the 13 retransmissions are required in anyseven-day period, the MIU will automatically reconfigure its links andselect a new primary collector using the procedures previouslydescribed.

An ACK packet is sent after receipt of a successful transmission. Thisstops an MIU from transmitting again after its transmission issuccessfully received. This reduces the number of units that willattempt to transmit during each successive time period. Because of thereduced number of units transmitting, the length of the subsequent timeperiods can be reduced and optimized. In the case where up to fourtransmissions are allowed, the first time period is typically half ofthe total time of cumulative length of all of the time periods.

In other embodiments, if the MIU goes for three consecutive days withoutreceiving an ACK from the collector with the 1st transmission of thatday, it will skip trying during the first time period. If the successrate for the previous ten days falls below 75%, the MIU will skip thefirst time period. If the success rate is still below 75%, the MIU willskip the first two time periods. If the MIU goes for more than 10 dayswithout an ACK, the MIU will revert to a one-way communication mode. Aslong as the MIU can receive the time from the collector to keep itsinternal system clock set, the MIU will continue to take the normal fourreadings a day in the one-way mode.

In some embodiments, the system shall operate in a frequency range of450-470 MHz. If operating in a duplex mode, the TX and RX channels areon different frequencies that are typically least 5 MHz apart. Thesystem may also change frequencies in simplex mode as well. In theseembodiments, the MIU can be programmed for multiple frequencies forcommunication. The collector can request the MIU to change frequency ituses. Once changed, the MIU will attempt to make contact with thecollector. If contact cannot be made within one hour, the MIU willrevert to the last frequency where contact occurred with the collector.In alternative embodiments, the MIU will remain on the new frequency andif communications with the collector are not established, the MIU willoperate as a one-way MIU on the new frequency. In other embodiments, theMIU can be programmed to determine if a new frequency should be tried ifcertain conditions happen. For example, the MIU will change frequencyand attempt to establish communications on the new frequency ifcommunications is lost for a certain period of time on the originalfrequency.

In the 450 MHz frequency band, governmental regulations have differentlimitations on power and antenna height for different frequencies. Someembodiments of the present invention take advantage of these rules foruse in a two-way system. In this embodiment, the MIU would be atransceiver, where the transmitter is on a low power channel and thereceiver is on a high power channel. The collector would receivetransmissions at low power on the low power channel, while thetransmitter of the collector would operate at high power on the highpower channel.

FIG. 3 shows a sequence diagram of a data transmission packet for oneexample of the present invention. Further, FIGS. 4 a-4 d show detailedsequence diagrams of various examples of transmission packets that willbe explained below. The system can include verification data in themessages transmitted within the network. This allows the system toverify that the data received is good and that no transmission errorshave taken place. The present invention combines the use of a check sumvalue (i.e., cyclic redundancy check or CRC) that is calculated from thecontents of the data and the system or Utility ID. The collector has thesystem or Utility ID stored and can recreate the CRC value with the datareceived to verify that the transmission is good. The system or utilityID is not transmitted as part of the message even though it is used inthe CRC calculation. This allows systems that are in proximity to eachother to operate without the messages being received with correct CRC bythe other utility. It also eliminates the need to transmit the utilityID which reduces the message length. Reduced message length is importantsince it reduces power consumption of battery powered MIUs and alsoreduces the probability of messages colliding due to the reduction intransmission duration. Because the Utility ID is not transmitted, itbecomes more difficult for an unintended recipient to decode the datawith correct CRC.

The present invention sends the usage profile data value as a percentageof daily consumption that occurred each hour. By using the percentage ofusage, the data packet does not have the issues of resolution. Forexample, if a water utility customer used between 0 and 2 gal per hourduring a 24-hour period, the measured value of the consumption per hourwould need to be to the nearest 0.1 gal to be meaningful. This wouldrequire 2 digits of resolution. If the next day, the same customer usedbetween 0 and 5,000 gal per hour, it would take 6 digits to report theconsumption to the nearest 0.1 gal. This level of resolution would mostlikely not be needed. By sending the percentage used each hour, twodigits are all that would be required for both of these cases.

If the system uses one byte (8 bits) of data, there are 256 uniquevalues to represent the percentage used each hour. This would normallygive us percentage usage value to the nearest ½%. The value of 0% is aunique case. Both where the total consumption for the day is zero andwhere the usage during a time period is 0% (to the nearest ½%). Takingthe case where the value of the usage to the nearest ½% is zero, thiscould be the result of the usage truly being zero or the usage was lessthan 0.25%. While the amount of usage may not be significant, the merefact that there was usage may be significance such as in leak detectionanalysis. For this special case we will designate a unique value torepresent a usage of zero and not just 0%. In another example where thereading for the total consumption is 0 for the 24 hour time periodoccurs when each hour has used an equal amount. For this special case,the system will assign a unique value to represent a uniform usage forthe entire 24 hours. This will reduce the necessary message length.

Once the information is received at the host computer, the totalconsumption registered on the meter is compared to the previous daystotal consumption registered on the meter. The percentage value ofconsumption can be converted to actual usage. As an alternative, theprevious day's total consumption registered on the meter, or the totalconsumption for that 24-hour period could be included with thetransmission. Because a value of 0% is less than ¼% (otherwise it wouldhave been recorded as ½%) and more than 0 consumption, it will assign ita value of ⅛%. When the percentage used in each hour is totaled, it maybe more or less than 100% due to rounding error. Because this botherssome users, the values will be adjusted at the host so the total willcome to 100%.

As an alternative to percentage values, a set number of digits could besent showing either consumption per hour or the meter reading. Themultiplier for the digits would be adjusted according to the consumptionused that day. For example, if 2 digits were being sent for each hourand the total consumption was 68,034 gal, the resolution would be to thenearest gallon. If the total consumption were 00.864 gal, the resolutionwould be to the nearest one hundredth gallon.

The profile packet is a packet that can be programmed in the MIU to betransmitted once per day. The operating scenario for use of the profilepacket would be to read at the zero hour (midnight) every day. Thisreading would be sent on a daily basis in the normal read packet. Ifflow profiling were enabled, the MIU would take the zero hour read andhourly reads during the day. Hourly consumption information would bestored. After twenty-three hourly reads the next zero hour read wouldoccur. At this point the MIU has two zero hour reads and 23 hourlyreads. The total consumption would be determined by the difference ofthe zero hour reads (Z2−Z1) unless reverse flow occurred during periodsof the profile. In this case, the consumption will be the absolute valueof the flow in each period so that if negative flow occurs it is treatedas forward flow.

The percentage of the total consumption used during each hour would becalculated as Cn/(Z2−Z1), where Cn is the consumption data for thecalculated hour. For periods with positive flow, the result of thiscalculation is an 8 bit value that represents 0-100% in 0.5% increments,(0-200). If the positive flow is more than 0 but less than 0.25% the 8bit returned value will be 255. This indicates low flow but not zero. Ifzero consumption is registered in all periods, then the totalconsumption is shown as zero and all periods return a zero value. Forperiods with negative flow, the result of this calculation is an 8 bitvalue that represents 0-100% in 2% increments shown as (201-250).Reverse flow of less than 2% is shown as zero flow. In all cases therewill be 24 of these 8 bit values that will be generated and transmittedas a profile packet.

In some embodiments, the system timing may be modified to improve thenetwork performance. The system time is typically controlled by the hostcomputer system. This time is passed to the collectors duringcommunications to the MIU from the collector. The MIU uses the systemtime to schedule a meter reading schedule and to schedule transmissionsand retransmissions to the collectors as well as other features andfunctions. The time passed from the host computer does not have tocorrespond to actual time but can be a “System Time”. The advantage ofhaving an independent system time is that the MIUs can operate in thesame manner with regard to the system time but the system can beoptimized to accomplish various goals. In this embodiment, the systemtime has a point where each daily period begins called the zero hourpoint. The zero hour point for the system can be set by the host to beany actual time during the day. By setting the zero hour to particulartime, numerous system parameters can be optimized. For example, the zerohour can be modified by one hour to accommodate daylight savings timeshifts such that the zero hour read occurs at the same hour each dayregardless of the state of daylight savings time. Additionally, if it isfound that the RF link performance is better at a particular time ofday, the zero hour can be shifted to allow the initial transmissions tooccur during this optimum time period. This would reduce the need forretransmissions and improve system packet success rate performance andbattery life. In another example, the customer may want to capturebilling data by a fixed time of day. Having the MIU transmissioninterval end just prior to the billing capture time would provide themost recent data to the billing system. It should be apparent that otheraspects of the system may be optimized by varying the system time inrelation to the actual time.

In alternative embodiments, there are times when it is desirable tocommunicate with the MIU from another device other than the collectorsuch as a hand held or notebook computer. This can occur before the MIUhas been programmed with the correct frequency or when the frequencyprogrammed in the MIU needs to be changed. At these times, it isdesirable to use the wireless RF link built into the MIU. The problemoccurs when the frequency and power level of the RF link are licensedand the MIU does not know the frequency that has been assigned, or theMIU is at a location other than the location that has been licensed.When activated, the MIU listens on a predetermined frequency. Thealternative device then communicates with the MIU at reduced the powerlevel to a level that does not require a license.

In other embodiments, a data transmission may use a unique preamblepattern to indicate the beginning of the data transmission and use aninversion of the unique pattern to indicate the end of the datatransmission. In this embodiment, the preamble pattern is different fora data encoding pattern.

In other embodiments, the primary collector may transmit a systemmaintenance message containing the status of the MIU to an installerduring the installation process. Additionally, the system firmware andsystem configuration settings for the MIU may be periodically upgradedvia maintenance radio transmissions. Also, temporary configurationcommands may be transmitted within an acknowledgement signal to the MIU.These temporary configuration commands will expire after a designatedtime period and the MIU will revert to a normal operationalconfiguration.

In other embodiments, the system may record and compare communicationlink quality among the data collectors and use this information formaintenance. For example, the system could monitor system noise versusthe time of day and adjust the data transmission time for when the noiseis minimal, in other embodiments MIU battery usage is tracked andrecorded for maintenance purposes. In this embodiment, battery usage maybe recorded as the depth of discharge of the battery.

In other embodiments, the detection of alarm conditions at an MIU iscontrolled by the host computer. For example, the host may enable,disable or delay the alarm transmission from the MIU. The collect may beinstructed to forward the alarm data packet directly to the hostimmediately upon receipt from the MIU. In an alternative embodiment, thetransmission of an alarm data packet may be delayed for some period toavoid data collisions.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed here.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A method of communicating data for a utilitymeter reading system, comprising: defining data collected from a utilitymeter by a meter interface unit as fractional or percentage value ofusage over a predetermined period of time; and transmitting said defineddata from said meter interface unit over a communications network. 2.The method of claim 1, where the percentage or fractional value of usageis an absolute value of usage so that a reverse usage may be shown as anegative value of usage.
 3. The method of claim 1, wherein saidpredetermined time period is one hour.
 4. The method of claim 1, whereinsaid data is defined digitally by a predetermined number of bitsproviding a data resolution, and further comprising distinguishingbetween a non-zero value of usage less than the lowest non-zero valuewithin the data resolution and an actual usage or zero.
 5. The method ofclaim 1, further comprising receiving said transmission over acommunications network and converting said defined data to an amount ofa standard unit of measure.
 6. A method of communicating data for autility meter reading system, comprising: collecting data from a utilitymeter with at least one designated meter interface unit (MIU) where thedata comprises utility usage defined as a fractional or percentagevalue; transmitting the data via a communication link between an MIU anda data collector; and transmitting the data from the data collector to acentral host computer.
 7. The method of claim 6, where the percentage orfractional value of usage is an absolute value of usage so that areverse usage may be shown as a negative value of usage.
 8. The methodof claim 6, wherein said data is defined digitally by a predeterminednumber of bits providing a data resolution, and further comprisingdistinguishing between a non-zero value of usage less than the lowestnon-zero value within the data resolution and an actual usage of zero.9. The method of claim 6, further comprising receiving said transmissionat said data collector and converting said defined data to an amount ofa standard unit of measure.
 10. The method of claim 6, furthercomprising receiving said transmission at said host computer andconverting said defined data to an amount of a standard unit of measure.